As a test, modify your mount on the client side to:

sudo mount -t nfs -o intr,hard,timeo=14,rsize=8192,wsize=8192 

or, if you put it in fstab on the client side:

remoteserver:/remote/path /local/path nfs rsize=8192,wsize=8192,hard,timeo=14,intr 0 0